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At least 145 records · Page 8Linked to original sources
PubMed1993

Dependence of the multiplicities of secondary particles on the impact parameter in collisions of high-energy neon and iron nuclei with photoemulsion nuclei.

A method is proposed for finding the dependence of mean multiplicities of secondaries on the nucleus-collision impact parameter from the data on the total interaction ensemble. The impact parameter has been shown to completely define the mean characteristics of an individual interaction event. A difference has been found between experimental results and the data calculated in terms of the cascade-evaporation model at impact-parameter values below 3 fm.

Elementary Particles↗
PubMed1997

How should brain nuclei be delineated? Consequences for developmental mechanisms and for correlations of area size, neuron numbers and functions of brain nuclei.

The measurement of the size of brain areas and their neuron numbers depends on the delineation of the boundaries of a brain area. The comparison of cytoarchitectural, cytochemical and connectional delineation of a brain area, such as the vocal control nucleus HVC (nucleus hyperstriatalis ventralis, pars caudalis) of songbirds, shows that the estimated size of a nucleus depends on the delineation criterion. In correlation, the cytoarchitectural, cytochemical and projection properties of the same brain area change independently both during development and in adulthood. This needs to be considered in cross-species, intersexual, developmental and temporal comparisons of brain areas. The combination of cytoarchitectural criteria with area-specific cytochemical and connectional markers to delineate the boundaries of a brain nucleus gives new insights into neural plasticity and parcelation of brain areas.

Animals↗
PubMed1975

Protein migration into nuclei. I. Frog oocyte nuclei in vivo accumulate microinjected histones, allow entry to small proteins, and exclude large proteins.

A technique is presented which enables one to measure the extent to which a protein enters and accumulates in the nucleus of the frog oocyte. In this method, the protein, labeled with 125-I, is microinjected into the oocyte. After incubation, the oocyte is manually enucleated and the radioactivity in the nucleus and cytoplasm is determined. Using this technique, proteins lighter than 20,000 daltons were found to enter the nucleus and completely equilibrate between the nucleus and cytoplasm within 24 h. The entry of proteins heavier than 69,000 daltons was severely hindered. Histones and histone fractions entered as quickly as other small proteins, but, in contrast to these proteins, they accumulated in the nucleus to different extents, depending on the total amount of histone injected into the oocyte and the identity of the histone. Evidence is presented that histone fractions compete with each other for accumulation in the nucleus.

Animals↗
PubMed1975

Protein migration into nuclei. II. Frog oocyte nuclei accumulate a class of microinjected oocyte nuclear proteins and exclude a class of microinjected oocyte cytoplasmic proteins.

Nuclear contents or cytoplasm from Xenopus oocytes labeled with (35-S)methionine or (3-H)proline (donor oocytes) were reinjected into unlabeled oocytes (recipient oocytes). The radioactivity injected as nuclear contents was found to enter and accumulate in the recipient oocyte nucleus. In contrast, the radioactivity injected as cytoplasm was found to enter but not to accumulate in the recipient oocyte nucleus. Sodium dodecyl sulfate (SDS) gel electrophoresis of the nucleus and cytoplasm of donor oocytes revealed the existence of three classes of labeled proteins in these oocytes: those proteins found predominantly in the nucleus (N proteins), those found predominantly in the cytoplasm (C proteins), and those found in both the nucleus and cytoplasm at similar concentrations (B proteins). SDS gel electrophoresis of the nucleus and cytoplasm of recipient oocytes showed that N proteins entered and accumulated in the nucleus but that B proteins partitioned about equally between the nucleus and cytoplasm. A similar analysis of oocytes injected with labeled cytoplasm showed that C proteins did not enter the nucleus but again B proteins partitioned about equally between the nucleus and cytoplasm.

Animals↗